MacBook Pro 13" mid 2012 wavy Backligh issue

the other day i was changing thermal past on cpu and and i forgot to unplug battery and she i was disconnecting lvds cable i probably short the power of lcd something like that -- the screen was white than you turn machine and you could see vertical lines if you look from top angle , so i took it to the shop and the guy fixed this problem , display work now but there is a wavy lines on the bottom of display like if not all leds working , i asked the guy about this and he told me that the problem in display module , so i bought a new display module , but on the new module is absolutely the same thing , not sure where to go from this ,on schematic i see this LP8550 controller i guess. if this would be broken ,i mean could it be part broken like not fully ,maybe you guys have experience in this and could help me

one the pic i show what the guy did to make display work again and what i don't like to see is that just Thin wire,, is this even okay ? or this thing that died there had zero resistance anyway ?

2 Respuestas

Looks like your original issue was with L9004 burning out, which causes a white screen. Can't see clearly from the picture, but usually you do have to solder a new ferrite bead and add a wire too, when it burns it nearly always destroys 1 or both solder pads for the component.

Regarding this issue, I would firstly check both sides of the LCD cable (make sure no melted plastic, pins aren't chipped/bent and the gold dots on the bottom of the pins are not dull looking) and also clean this using isopropyl. I would then use a soft brush and isopropyl to clean inside the LCD connector. This issue is nearly always caused by debris or dried solder flux inside the connector/on the cable, I have had the same issue when soldering around the connector before, flux has always caused interference with this. This will especially be the case if these backlight marks where not visible when you had the initial white screen issue.

If it is not this, it will likely be the LED return resistors, but it is very rare for these to have issues unless they were liquid damaged, knocked or soldered before. Give the connector and cable a good clean first, which should sort your issue.

Yes when it was just a white screen its didn't had those issues , ill give it a try with cleaning , but i also checked resistors and all of them short to ground .. does it have to be like that ? or they supposed to have value ?

No they should not be. I would recommend removing one of them and finding out which pad the short is located. This will allow you to determine whether the backlight IC is shorting it or the LCD connector/cable.

Shine a light inside the LCD connector to see if it looks melted or different to the rest of the connector. Check the LCD cable, and check for a short on the resistor with the LCD cable disconnected. I imagine it's more likely for it to be an issue LCD connector/cable side, I have never the backlight IC just short these LED return resistors to ground, but still light up the screen.

Such a weird case ... I wish I could make a photo of what I see inside the connector , as far as I see they all gold looking , as for resistors when I check those that Oros told me to check they all short to ground but display works no idea how then .. I cleaned as good as I only could and it seems pretty clear gold shiny inside and on LCD cable connector

Remove one of the resistors and measure for a short on both solder pads. This will tell you if the short is coming from the backlight IC or the LCD conn/cable, and will allow you to troubleshoot further.

i think i might be wrong and they all have 0 ohms , which makes me think it short to ground , than i put on beep mod and check both pads on the resistor it beeps so its short to ground to me .. today i was scared to try your idea .. i have a tough that it might be LP8550 thats broken , i added 3 more pics of example how i measure

Out of the 3 new pics, the 1st pic is correct (that side should short to ground), the other 2 pics shouldn't be shorting to ground (although, I'm assuming the 2nd pic you are measuring for a short to both sides individually, you are not measuring resistance across the resistor, since it is a 0ohm resistor and will beep).

The resistor in 1st/3rd pic is 10kohms, check this is reading correct. If it is, I would remove the backlight IC to see if the short has gone, because it looks like liquid has been in that area.

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